Among plastic materials, polyimide is excellent in properties such as heat resistance, insulating property, solvent resistance, and low temperature resistance. Thus, the polyimide is used for electric and electronic component materials. Particular examples of the electric and electronic component materials using polyimide include a flexible print wiring board, a base film of a TAB carrier tape, a wire coating agent for an aircraft or the like, a base film of a magnetic recording tape, a wire coating agent for a superconducting coil, and the like. For each purpose of use, polyimide film suitable for the purpose is selected as necessary. With reduction in the size and thickness, electric and electronic components have finer circuit wirings. Therefore, change in the size of the component may cause malfunction such as wire breakage and short circuit in the circuit having finer wirings.
Incidentally, the polyimide film is produced as follows: a polyimide precursor solution composition prepared as a polyimide precursor is mixed with a chemical imidization solution including a dehydrating agent and an imidization catalyst, and the mixture is continuously extruded from a slit die in a flat thin film manner onto a support such as a drum and an endless belt, and the resultant is solidified through drying and cooling so that its self supporting property is kept while promoting imidization, and then the solidified resultant is further heated. There is also an method in which: a polyimide precursor composition prepared as a precursor of the polyimide film is flown in a casting manner by using a slit die, and the resultant is completely imidized through film formation, a heating treatment, and a drying treatment, thereby producing the polyimide film. However, in this production method, a large quantity of heat and time is required in order to remove a solvent having high affinity with respect to the polyimide precursor, so that this raises such a problem that the productivity of the method is low. While, if the heat quantity is increased in order to keep and improve the productivity, this raises such a problem that a film quality such as a mechanical property and adhesive strength drops.
Incidentally, Patent Document 1 discloses a polyimide film obtained by carrying out ring closure of polyamide acid obtained by mixing pyromellitic dianhydride and 4,4′-diamino diphenyl ether and describes that a chemical ring closure agent and a catalyst are used to carry out imidization, but does not describe that ethyl pyridine is used as the catalyst. [Patent Document 1] Japanese unexamined Patent Publication No. 118386/1995 (Tokukaihei 07-118386)(Publication date: May 9, 1995).